Method of inhibiting the automatic stop control system of the heat engine of a vehicle in congested traffic

ABSTRACT

The invention relates to a method of controlling the stopping and starting of a heat engine ( 2 ) of a vehicle. The invention is of the type in which (i) it is necessary for the vehicle to be in an engine stop request phase, and not in pre-defined operating conditions that oppose the stopping of the engine ( 2 ), in order for the engine ( 2 ) to be stopped or (ii) it is necessary for the vehicle to be in an engine start request phase, and not in pre-defined operating conditions that oppose the starting of the engine ( 2 ), in order for the engine to be started. The invention is characterized in that the vehicle operating conditions that oppose the stopping of the engine ( 2 ) comprise slow congested traffic conditions constituting specific identification criteria.

The present invention concerns a method of controlling the automatic stopping and starting of a heat engine with which a motor or road vehicle is equipped.

The present invention concerns more particularly the non authorization of the stopping of the engine in congested traffic.

Manufacturers of vehicles equipped with heat engines, such as motor or road vehicles, are always seeking technical solutions likely to reduce the consumption and the emissions of pollutants of these engines.

Among the various solutions developed to this day, a system has been proposed that triggers the automatic stopping of the engine in all the phases of use of the vehicle in which the operation of the engine is not necessary, such as the phases in which the vehicle is temporarily stopped and in which the engine keeps idling anyway, then performs the automatic starting of the engine when the driver wishes to have the vehicle start off again.

This solution of automatic stopping and starting of the engines, also called by Anglo-Saxons “Stop and Start” or “Stop and Go,” has an important potential for reduction of the consumption of the engines because it is estimated that, on average, for a given journey, a vehicle is stopped with the engine in idle for about 20% of the time.

A “Stop and Start” system comprises generally a computer to control automatically the stopping and starting of the heat engine from appropriate information on the operation of the vehicle. This computer comprises notably means adapted to identify an engine stop request phase, means adapted to identify an engine stop authorization phase during which the stopping of the engine is actually possible, and means for performing the actual stopping of the engine if the conditions “vehicle in engine stop request phase” and “vehicle in engine stop authorization phase” are both met.

In the same manner, a “Stop and Start” system comprises notably means adapted to identify an engine start request phase, means adapted to identify an engine start authorization phase during which the starting of the engine is actually possible, and means for performing the actual starting of the engine if the conditions “vehicle in engine start request phase” and “vehicle in engine start authorization phase” are both met.

Any time period during which the driver indicates his or her desire to stop the engine of his or her vehicle is called “engine stop request phase,” wherein the vehicle can be stopped or still moving. Such a desire to stop the engine can be characterized by various criteria, such as the operation of the brake pedal of the vehicle by the driver.

Any period during which the operation of the vehicle does not require the operation of the engine, and thus, authorizes its stopping, is called “engine stop authorization phase.” The conditions of operation of the vehicle requiring the operation of the engine, and this, while the vehicle is in engine stop request phase, can concern the specific operation of an equipment of the vehicle as well as relate to the driving pleasure only. These conditions opposed to the stopping of the engine are characterized by various criteria such as, for example, the temperature of the engine cooling water lower than a predetermined threshold. Indeed, an engine must reach a certain temperature to operate in an optimal manner, so that it is not opportune to delay the temperature increase of the engine by stopping it too early after it has started.

Any time period during which the operation of the vehicle requires the starting of the engine is called “engine start request phase.” The conditions of operation of the vehicle requiring such a start are inferred generally from the conditions opposed to the stopping of the engine.

Any period during which the operation of the engine does not prohibit the starting of the engine is called “engine start authorization phase.” The conditions of operation opposed to a start can be linked, for example, to the opened or closed state of the clutch and/or to the state of the transmission, with a gear being engaged or not.

The document WO-98/14702 describes a “Stop and Start” system. This system comprises an electronic card that controls the stopping and starting of the heat engine from information supplied by two sensors:

-   -   a clutch pedal position sensor;     -   a hand brake position sensor.

If the clutch pedal is not pushed down and if the parking brake is actuated, then the engine is stopped automatically. If the clutch pedal is pushed down and if the parking brake is released, then the engine is restarted automatically.

This system also uses an engine speed sensor that deactivates the electronic card if the engine speed is higher than a certain threshold and an engine temperature sensor that also deactivates the electronic card if the engine has not reached its operating temperature.

Such a system actually makes it possible to reduce the consumption of the heat engine while minimizing the idling operating phases of the engine. However, the reduction in consumption generated by such a system does not seem particularly optimized.

Indeed, the engine stop request phases are here simply limited to the periods when the parking brake is actuated. Regarding the engine start authorization phases, they are defined only from a very limited number of operating conditions of the vehicle opposed to a stopping of the engine, i.e., the “cold engine” operating modes or the high engine speed operating modes.

Thus, with such a system, any stopping of the vehicle for which the parking brake is not actuated does not trigger any stopping of the engine, whereas this type of stopping represents a high proportion of the phases where the vehicle is stopped. Indeed, drivers rarely actuate the hand brake in a situation of temporary stopping, such as when stopping at street lights.

Further, the solution described in the document WO98/14702 is purely material. As a consequence, its complexity and notably that of its electronic card increases rapidly when the number of items of information taken into account to perform the automatic stopping of the engine increases.

The patent application FR-A-2 816 891 filed by the Applicant describes a more sophisticated “Stop and Start” system that remedies the drawbacks of the previous systems by creating a system that makes it possible to implement substantially higher-performance automatic engine stopping and starting strategies.

The system for controlling the automatic stopping and starting of a heat engine, object of the application FR-A-2816891 comprises means for stopping and starting the engine, sensors of information on the state of the vehicle, means for controlling said means for stopping and starting the engine from the information of the sensors, and is characterized in that these control means comprise a computer containing an algorithm for controlling said engine acting as a function of the data supplied by said information sensors.

This system makes it thus possible to take into account a larger number of vehicle operating situations requesting the stopping of the engine, and thus to improve the gain in consumption generated by a larger number of engine stops, while taking into account a larger number of operating conditions of the vehicle opposed to the stopping of the engine, and this, so as notably to limit the possible impacts of stopping of the engine on the operation of the vehicle and on the driving pleasure.

Such a system makes it thus possible to solve in a simple way problems that call for more complex engine control strategies taking into account an important number of operating conditions of the vehicle.

However, it has been observed that new improvements were necessary to provide a better driving pleasure.

Indeed, in all the systems proposed to this day, the situations relative to congested traffic, notably when vehicles move at a crawl and are subjected to frequent stops, situations also called traffic blockages or traffic jams, are not considered, which has the effect, for such traffic conditions, of generating a succession of engine stops that are short and useless, or even penalizing in terms of fuel consumption.

A goal of the present invention is thus to improve further the method of controlling the automatic stopping and starting of an engine, by proposing a method for automatically controlling the stopping and starting of an engine adapted to discriminate traffic jam situations and that takes them into account to define the engine stop authorizations.

The method according to the invention concerns the control of the stopping and starting of a heat engine with which a vehicle is equipped, of the type according to which it is necessary that the vehicle be in an engine stop request phase and not in the predefined operating conditions opposed to the stopping of the engine for the stopping of the engine to be controlled, or in which it is necessary that the vehicle be in engine start request phase and not in the predefined operating conditions that are opposed to the starting of the engine for the starting of the engine to be controlled.

According to the invention, the method of controlling the stopping and starting of a heat engine is characterized in that the operating conditions of the vehicle opposed to the stopping of the engine comprise the conditions of slow traffic of the traffic jam type, these conditions of slow traffic being the object of specific identification criteria.

According to another characteristic of the control method object of the present invention, the conditions of slow traffic are identified from the analysis of the time periods separating the engine stop controls from one another.

According to another characteristic of the control method object of the present invention, the stopping of the engine can be controlled only if a time period of more than a predetermined threshold value has elapsed since the previous engine stop control.

According to another characteristic of the control method object of the present invention, the conditions of slow traffic are identified from the analysis of the duration of operation of the engine.

According to another characteristic of the control method object of the present invention, the stopping of the engine cannot be controlled as long as the duration of operation of the engine does not exceed a predetermined threshold value.

According to another characteristic of the control method object of the present invention, the conditions of slow traffic are identified from the analysis of the distances covered by the vehicle.

According to another characteristic of the control method object of the present invention, the stopping of the engine cannot be controlled as long as the distance covered since the last time the engine has been started is more than a first threshold value and less than a second threshold value.

According to another characteristic of the control method object of the present invention, the conditions of slow traffic are identified from the analysis of the speeds reached by the vehicle.

According to another characteristic of the control method object of the present invention, the conditions of operation of the vehicle opposed to the stopping of the engine comprise the moving speed of the vehicle of more than a threshold value, this threshold value being adapted to take into account the traffic conditions and notably a traffic jam situation.

According to another characteristic of the control method object of the present invention, as long as the speed of the vehicle since the last time it has been started has not exceeded a first predetermined threshold value, then the stopping of the engine can be controlled only if the speed of the vehicle is less than a second predetermined threshold value.

The invention will be better understood by reading the following description, given by way of example only and made in reference to the annexed drawings in which:

FIG. 1 is a view of a material architecture of the whole system for implementing the method according to the invention;

FIGS. 2 to 4 show the different steps of a schematic flow chart of the method according to the invention.

FIG. 1 shows various organs of a motor vehicle 1 equipped with a heat engine 2. In the passenger compartment of the vehicle, a switch 3 (with or without a key), disposed in the vicinity of the steering wheel 4, controls manually the starting and stopping of the engine 2, whereas means, such as a two-position switch 5 of the push button type, makes it possible for the driver to activate or inhibit the operation of the vehicle in the “Stop and Start” mode, i.e., in the automatic stopping and starting mode of the engine 2.

The vehicle comprises further a transmission mechanism whose gear lever 6 is shown, as well as a braking device controlled notably by a brake pedal 7.

Of course, these equipments are not limitative of the other equipments of the vehicle which have not been shown, such as, in particular, a clutch, an engine cooling fan system to cool the engine 2, an air conditioning device to cool/heat the passenger compartment, a power steering mechanism, etc.

The heat engine 2 is a standard engine of the multi-cylinder type with controlled ignition or compression ignition (diesel). These types of engines are well known and will not be described in further details. The operation of the engine 2 is controlled in a standard manner by an engine control computer 12 that drives notably the fuel flow rate.

The engine 2 cooperates with appropriate starting means such as a reversible rotating electric machine 8 forming alternator-starter. A transmission of movement, for example, via pulleys and belt, connects the rotor of the alternator-starter 8 to the crankshaft of the engine 2.

In a variant embodiment, the engine 2 can also cooperate with an additional starter, not shown, distinct from the alternator-starter 8.

The machine 8 makes it possible to transform a rotating movement of the inductor rotor, driven by the heat engine 2 of the vehicle, into an electric current induced in the coil windings of the stator. This current is then intended to supply electricity to the on-board network of the vehicle and to load the battery 9 of this vehicle.

The machine 8 can also constitute an electric motor or rotating electric machine and drive in rotation, via the rotor shaft, the heat engine 2 of the vehicle. Thus, the alternator-starter 8 can start the heat engine 2 of the motor vehicle.

This machine 8, for example, of the polyphase type, operates thus as an alternator, notably to load the battery of the vehicle, and as a starter, to drive the internal combustion engine, also called heat engine, of the motor vehicle so as to start it. To this effect, a power unit connected to the phases of the armature of the alternator is used as a control bridge of these phases in motor mode and serves as a rectifier bridge when the alternator-starter 8 operates in alternator mode.

Such a machine 8 is well known in itself and will not be described in further details. The document FR2842041, for example, describes such a machine.

The system implementing the method for automatically controlling the stopping and starting of the engine according to the invention comprises a computer 11 that drives, via the computers 10 and 12, the operation of the machine 8 and the stopping and starting of the engine 2, and this, from a certain number of items of information concerning the operation of the vehicle.

Indeed, the computer 11 cooperates with appropriate information sensors adapted to supply, in addition to the position of the switch 3 or of the button 5, the required information on the operation of the vehicle, such as the rotation speed of the engine 2, the speed of the vehicle, the distance covered, the position of the clutch pedal, the position of the accelerator pedal, the position of the gear lever 6, the position of the brake pedal 7 and that of the hand brake, the gear set in the gear box, the temperature of the engine cooling water, the loading state of the battery 9, the state of the air conditioning, the torque applied to the steering wheel by the driver, etc.

It is important to notice that the computer 11 according to the present invention is defined in a more general way as being any system in which a control algorithm can be implanted using programming means and containing at least a memory. A programmable logic array of the ASIC type could be used. This computer 11 can be specific as illustrated or it can be integrated into another computer, such as, for example, the computers 10 or 12, or it can be integrated into several computers.

The computer 11 performs a constant monitoring of the operation of the vehicle from a certain number of items of information transmitted directly by appropriate sensors or via other computers to which the computer 11 is connected, and when the engine is rotating, it checks whether the vehicle is or is not in engine stop request phase and in engine stop authorization phase, and it infers therefrom the stopping of the engine. In the same manner, the engine being stopped, the computer 11 checks from the information received whether the vehicle is or is not in start request phase and in engine start authorization phase, and infers therefrom the starting of the engine.

The engine stop request phases are defined by appropriate vehicle operating criteria combining the fact that the button 5 is in “not inhibited” position and that notably one of the following criteria is observed:

-   -   the position of the brake pedal goes from “not pushed” to         “pushed”;     -   the gear lever is in neutral.

With respect to the engine start authorization phases, they are defined from a certain number of criteria identifying predefined vehicle operating conditions opposed to the stopping of the engine 2.

Different types of vehicle operating conditions likely to define these authorization phases can be distinguished:

-   -   conditions linked to the vehicle itself, such as the needs of         the engine (water temperature, etc.), the needs for braking         assistance, the needs of the on-board electrical network, the         passenger compartment heating needs, etc.;     -   conditions linked to the driving pleasure, such as parking         maneuvers, etc.;     -   conditions linked to the driver.

With respect to the start request phases, they are inferred substantially from the conditions opposed to the stopping of the engine.

Turning to the conditions opposed to the start requests, they comprise notably situations linked to the transmission, such as the existence of a gear being engaged.

FIGS. 2 to 4 show an example of a control algorithm implementing the method according to the invention and contained in the electronic memories of the computer 11.

It is to be noted that the software architecture used to code the algorithm can be decomposed into two modules.

A first module, called low-level software, groups the controls relative to the material architecture used, such as the reading of a signal at one of the inputs of the microcontroller or the emission of an output signal. This low-level software is specific to the microcontroller used. The second module, called high-level software, is specific to the application implemented.

In the present invention, the second module is used to implant the management strategy of the automatic starting and stopping of the engine. It is performed in a programming language such as C.

Once the engine has been started and in the case where the switch 4 is in a position in which the automatic stop function of the engine is activated, the computer 11 checks regularly the operating state of the engine from the collected information, and thus performs the steps below in an iterative way.

Referring to FIG. 2, during the test step 100, the computer 11 checks whether the vehicle has entered a new engine stop request phase.

A stop request phase is identified, for example, if the driver pushes on the brake pedal and/or has shifted gears to neutral (gear lever in neutral position or in neutral) and if the button 5 is in activated or “not inhibited” position.

When a new engine stop request phase has been identified and during the whole time period that this stop request phase will last, i.e., the whole time period when the driver keeps his or her foot pushed on the brake pedal and/or keeps the gears in neutral and the button 5 is in activation position, the computer then checks whether the vehicle is or is not in engine stop authorization phase, and this during step 101.

Indeed, the actual stopping of the engine is controlled only if the operating conditions of the vehicle allow it, i.e., if the vehicle is not in any one of the predetermined conditions for which the stopping of the engine is not authorized.

If at least one of the operating conditions of the engine opposed to the stopping of the engine is verified, then the engine is not stopped, and the engine will not be stopped during the whole duration of the present vehicle stop request phase, even if the condition that initially does not authorize the stopping disappears before the end of this stop request phase. Thus, the process ends there and returns to step 100.

In the variant embodiment shown on FIG. 2, it will be possible also to authorize a stopping if the condition that does not initially authorize the stopping of the engine disappears before a time period or delay T counted from the entry into the vehicle stop phase has elapsed. This delay T calibrated as a function of the engine and of the vehicle concerned is generally comprised between two and ten seconds.

The conditions opposed to the stopping of the engine are thus tested one by one during the step 101, and if none of these conditions is met, the engine is then stopped at the step 102.

Referring to FIG. 2, it is visible that the step 101 thus consists in a series of tests 1011, 1012, 1013, 101 i . . . , each characterizing operating conditions of the vehicle for which the stopping of the engine is not authorized. These conditions will not be described further, except those object of the sub-step 1011, given by way of example, and those object of the sub-steps 1012 and 1013, relative to the present invention.

Thus, the sub-step 1011 concerns the “cold engine” operating conditions of the vehicle, characterized notably by a temperature of the cooling water lower than a calibrated threshold value. It is indeed important, notably for the depollution of the exhaust gases of the engine, to promote as much as possible the temperature increase of the engine, and thus, to prevent its stopping until it has reached a sufficient temperature.

Thus, the sub-step 1012 concerns the moving speed of the vehicle. The control of the stopping of the engine is not authorized as long as the moving speed of the vehicle remains higher than a given threshold value Vm. This calibrated threshold value Vm is generally comprised between four and ten kilometers per hour.

Thus, the sub-step 1013 concerns the slow traffic conditions notably of the “traffic jam” type. Indeed, during such traffic conditions, there occurs many short duration immobilization conditions of the vehicle during which it is not very pertinent to stop the engine.

In accordance with the invention, the method of controlling the engine performs the specific recognition of such slow traffic conditions, from appropriate characteristic items of information which are the frequency of the engine stop control, the duration of operation of the engine, the distance covered, or the speed reached by the vehicle between two stop phases. As a result therefrom, the step 1013 is decomposed into a succession of four sub-steps detailed at FIG. 4 in correspondence with the four criteria retained.

At the step 1013 a, the duration of operation of the engine is controlled. If the duration of operation of the engine since the last engine start control is more than a threshold value Tm calibrated as long as the duration of operation of the engine has not exceeded the threshold Tm since the last time the engine was started, then the stopping of the engine is not authorized. This calibrated time value Tm is generally comprised between one second and three minutes.

At the step 1013 b, the time elapsed between the engine stop controls is controlled. If the time elapsed since the last stop request is more than a threshold value Ts calibrated as long as the time elapsed since the last engine stop request has not exceeded the threshold Ts, then the stopping of the engine is not authorized. This calibrated time value Ts is generally comprised between one and thirty seconds.

At the step 1013 c, the distance covered by the vehicle since the last time the engine was started is controlled. If the distance covered by the vehicle since the last time the engine was started is more than a first threshold value L1 but less than a second threshold value L2 higher or equal to L1, then the stopping of the engine is not authorized. These threshold values L1 and L2 are calibrated and generally comprised between zero and two hundred meters.

At the step 1013 d, the speed of the vehicle is controlled. If the speed of the vehicle remains lower than a calibrated threshold value V1 since the last time the engine was started, then the stopping of the engine is not authorized as long as the moving speed of the vehicle remains more than a given threshold value Vme. This calibrated threshold value Vme, lower than Vm, is generally comprised between one and four kilometers per hour, with respect to the calibrated value V1, it is generally comprised between five and thirty kilometers per hour.

Thus, thanks to the implementation of the method according to the invention, it is possible to identify in a very precise manner the vehicle in slow traffic conditions, and then to perform the inhibition of the automatic stopping and starting function of the engine, and this, to provide the driver with a higher comfort in using the vehicle and to optimize the impact of the system on the fuel consumption.

Of course, the present invention is not limited to the particular embodiment described above, and thus, numerous changes or modifications can be made thereto without leaving the scope of the present invention.

Thus, the steps 1012 and 1013 d can be grouped by making the value Vm dependent on the speed reached by the vehicle since the last time it was started. 

The invention claimed is:
 1. Method of controlling the stopping and starting of a heat engine with which a vehicle is equipped, comprising: controlling stopping of the engine when the vehicle is in an engine stop request phase and not in predefined operating conditions opposed to a stopping of said engine, and controlling starting of the engine when the vehicle is in an engine start request phase and not in predefined operating conditions opposed to the starting of said engine, wherein said operating conditions of the vehicle opposed to the stopping of said engine comprise conditions of slow traffic, these conditions of slow traffic being the object of specific identification criteria, so that the engine is not stopped in the slow traffic conditions, wherein the operating conditions of the vehicle opposed to the stopping of said engine include: a condition wherein the moving speed of the vehicle is more than a first threshold value, wherein said first threshold value is more than zero, and a condition wherein the speed of the vehicle since the last time the engine has been started has not exceeded a second threshold value, wherein said second threshold value is more than zero, and the speed of the vehicle is equal or more than a third threshold value which is lower than the first predetermined threshold value, wherein said third threshold value is more than zero, so as to take into account the traffic conditions and notably a traffic jam situation.
 2. Control method according to claim 1, wherein the conditions of slow traffic are identified from the analysis of the time periods separating the engine stop controls from one another.
 3. Control method according to claim 2, comprising controlling the stopping of the engine only if a time period of more than a fourth predetermined threshold value has elapsed since the previous engine stop control.
 4. Control method according to claim 1, wherein the conditions of slow traffic are identified from the analysis of the duration of operation of the engine.
 5. Control method according to claim 4, comprising inhibiting the stopping of the engine as long as the duration of operation of the engine does not exceed a fifth predetermined threshold value.
 6. Control method according to claim 1, wherein the conditions of slow traffic are identified from the analysis of the distances covered by the vehicle.
 7. Control method according to claim 6, comprising controlling the stopping of the engine as long as the distance covered since the last time the engine has been started is more than a sixth threshold value and less than a seventh threshold value.
 8. Control method according to claim 1, wherein the conditions of slow traffic are identified from the analysis of the speeds reached by the vehicle.
 9. Control method according to claim 8, wherein as long as the speed of the vehicle since the last time it has been started has not exceeded a first predetermined threshold value, the method comprises controlling the stopping of the engine only if the speed of the vehicle is less than a second predetermined threshold value.
 10. Control method according to claim 1, wherein the first threshold value is a predetermined threshold value.
 11. Control method according to claim 10, wherein the first threshold value is comprised between four and ten kilometers per hour.
 12. Control method according to claim 10, wherein the second and third threshold values are calibrated values.
 13. Control method according to claim 12, wherein the first threshold value is comprised between four and ten kilometers per hour, the second threshold value is comprised between five and thirty kilometers per hour and the third threshold value is comprised between one and four kilometers per hour.
 14. Control method according to claim 1, wherein the first threshold value is comprised between four and ten kilometers per hour.
 15. Control method according to claim 1, wherein the second and third threshold values are calibrated values.
 16. Control method according to claim 15, wherein the second threshold value is comprised between five and thirty kilometers per hour and the third threshold value is comprised between one and four kilometers per hour.
 17. Control method according to claim 1, wherein the operating conditions of the vehicle opposed to the stopping of said engine also include: a condition wherein a time period since the last time the engine was in engine stop request phase has not exceeded a fourth predetermined threshold value, and a condition wherein a duration of operation of the engine since the last time the engine has been started has not exceeded a fifth predetermined threshold value, a condition wherein a distance covered since the last time the engine has been started is more than a sixth threshold value and less than a seventh threshold value. 